The present application relates to the field of imaging, and, in particular, computed tomography (CT) imaging where volumetric data of an object under examination is generated. It finds particular utility in medical applications, where a pre-object filter may be utilized to reduce a dosage of radiation applied to a patient. However, it may also find utility in security and/or industrial applications, where radiation is utilized to examine and/or image an object.
CT imaging modalities are useful to provide information, or images, of interior aspects of an object under examination. Generally, the object is exposed to radiation photons (e.g., such as X-rays, gamma rays, etc.), and an image(s) is formed based upon the radiation absorbed and/or attenuated by the interior aspects of the object, or rather an amount of photons that is able to pass through the object. Traditionally, the image(s) that is formed from the radiation exposure is a density image or attenuation image, meaning the image is colored/shaded as a function of the respective densities of sub-objects comprised within the object under examination. For example, highly dense sub-objects absorb and/or attenuate more radiation than less dense sub-objects, and thus a sub-object having a higher density, such as a bone or metal, for example, will be shaded differently than less dense sub-objects, such as muscle or clothing. However, more recently, multi-energy imaging systems (e.g., such as dual-energy CT scanners) have been utilized to discriminate sub-objects based upon more than density. Such systems are typically configured to distinguish sub-objects based upon density and other physical characteristics, such as atomic number, for example.
In some applications, such as medical imaging, it may be desirable to reduce (e.g., to a minimum) the dosage of radiation applied to a patient while achieving a desired image quality. Numerous techniques have been developed to preserve/improve image quality while reducing dosage to a patient. For example, current modulation techniques (e.g., which modulate a current applied to a radiation source) and iterative image reconstruction techniques have provided ways to preserve/improve image quality while reducing dosage to a patient. Another technique for achieving such a result is through the use of a pre-object filter, such as a bowtie filter, for example, which is inserted into a radiation beam path to shape a profile of the radiation beam to facilitate reducing dosage to a patient. Such pre-object filters have proven effective for reducing dosage (e.g., by up to 50% or more). However, due to their high cost and complexity, such pre-object filters are typically not tailored (e.g., optimized) for respective anatomical regions and/or patient sizes. For example, conventional scanners typically have, at most, two pre-object filters. A first pre-object filter corresponds to an average head size of a human patient and a second pre-object filter corresponds to an average body size of a human patient. As such, the pre-object filters may not be well suited for patients not conforming to average sizes (e.g., such as larger/smaller adults, children, etc.), causing radiation flux to less precisely match some patients relative to others.